1. Field of the Invention
The present invention relates to a seismic energy dissipation device, and in particular to a seismic energy dissipation device having excellent energy dissipation capacity.
2. Description of Prior Art
During the past few years, it has been realized that earthquake-induced energy in building structures can be effectively dissipated by the use of certain structural devices. For example, one such device, known as bolted X-shaped steel plate added damping and stiffness (ADAS) devices, was disclosed by Whittaker et al. in "Seismic Testing of Steel Plate Energy Dissipation Devices", Earthquake Spectral 7(4): at 563-604, EERI (Nov. 1991). Recent experimental results obtained by the National Taiwan University also indicate that properly welded steel triangular-plate added damping and stiffness (TADAS) devices can sustain a very large number of yielding reversals without any sign of stiffness or strength degradation.
FIG. 1 is a perspective exploded diagram of a typical welded TADAS device. The TADAS device comprises a plate 10, a plurality of triangular plates 20, a plurality of blocks 30, a base 40, and a plurality of pins 41. The narrower ends of the triangular plates 20 are respectively connected to the blocks 30, while the wider ends are connected to the plate 10. The blocks 30 are pivoted to the base 40 through the pins 41. FIG. 2 shows the assembly of the typical welded TADAS device.
The typical welded TADAS device has significant drawbacks. It has rigidly precise requirements for the distance between the blocks 30 to allow the pins 41 to be put into the holes 31, 42. However, such strict precision is difficult to attain because the plate 10, the triangular plates 20, and the blocks 30 are welded together (it is noted that casting them as a single piece can be done with greater precision but results in less ductility, an undesirable characteristic for an earthquake-resistance device). Therefore, assembling the welded TADAS is troublesome.
When a transverse force is applied, the triangular plates 20 can deform well into the inelastic range since the curvature distribution is uniform over the triangular plate height. However, the spacing between the triangular plates decreases as the device deformation increases. Thus, eventual collisions between the blocks may occur as shown in FIG. 3. This changes each end of the triangular plates from a roller to a more-fixed boundary condition, and results in sudden increases of the force response of the device after the collisions of the blocks. In other words, when the blocks 30 collide with each other the original design of the triangular-plate device fails to work creating a dangerous condition in the building structure.